1. Field of Invention
The present invention relates to automatic fastener systems of the type which automatically feed, and then drive, a screw or similar fastening means into a workpiece, and more particularly to an automatic screwdriver system of this type which has screw detection means to indicate when a screw is present in the screwdriver head, as well as automatic advance and retract means, and is particularly adapted, therefore, to be mounted and used in robotic manufacturing systems.
The improvements over the prior art disclosed in the present application relate to a particular screw sensing means to detect when a screw is present in the system so the automatic advance and retract means will know when it may operate without seriously damaging the screwdriver system. The automatic advance and retract means operates by use of proximity switches, and this, in connection with a signal received when a part is present, can be utilized by relay logic, or a programmable controller, to operate the system.
2. Description of the Prior Art
Automatic screw feeders used by the worker on the production line have been known in the art for some time. One such automatic screw feeder is sold under the name "Acra-Feed", and is manufactured by the AIM Corporation of Portland, Oreg. The purpose of these units is to feed a screw pneumatically to a screwdriver head, which then electrically or pneumatically drives the screw with operator assistance; thus, relieving the worker of the tedious task of constantly having to pick up and locate a new screw each time one is to be inserted in a part. However, it can be seen that these units still require the presence of the worker to hold the screwdriver head in proximity to the work, determine when a screw has been fed into the screwdriver head, and then hold the unit when the screw is driven. Thus, while these devices are called automatic screw feeders, they certainly cannot be called "automatic screwdrivers".
Many attempts have been made to eliminate the need for the operator to actually drive screws, or other fasteners, as a means of connecting parts together on the production line. However, until the present invention, there have been many problems which have remained unsolved in the art. Two of the most serious problems were how to accurately advance and retract the driving head automatically, and, perhaps more importantly, how to detect, in the absence of the worker being present, when a screw, or other fastener, was present in the driving head to prevent destruction of the apparatus should it try to advance into the workpiece without a screw present. Thus, the dual problems of screw detection and driver movement have remained unsolved in the prior art up until the present time.